Gay rights advocates are declaring a cautious victory in the nation's capital this week.

A bill legalizing same-sex marriage in Washington, D.C., is expected to pass a City Council vote on Tuesday.

David Catania, the openly gay councilman who drafted the bill, says he has been waiting for this day for a long time.

"After a year of planning and working and strategizing and organizing and cajoling and discussing it, I can finally see that the end is in sight," Catania says.

The mayor has already committed to signing the bill, but opponents are vowing not to give up the fight against it. And because laws in the District of Columbia are subject to congressional review, even if the bill passes on Tuesday, it won't be too late for opponents to lobby for it to be overturned.

'A Bright Line Around The Marriage Issue'

Organizations that oppose the law, like the Catholic Church, are making their voices head even as the vote draws near.

Susan Gibbs, spokeswoman for the Archdiocese of Washington, says the church wants stronger religious protections in the bill.

"Being gay is not against church teaching, but we do understand marriage in a specific way, and we need to be able to follow that belief," Gibbs says.

The church believes that marriage is between a man and a woman — a belief shared by the National Organization for Marriage.

President Maggie Gallagher says the advocacy group is planning a battle against the legislation in Washington. It's a battle the group has already fought in other states this year.

New York and Maine recently rejected same-sex marriage, and New Jersey just postponed a vote on the issue. Gallagher says it has been an excellent few months for those who oppose same-sex marriage.

"It's true that Americans are a tolerant and welcoming people, and that includes gay people," says Gallagher. "But they draw a bright line around the marriage issue."

'Clear Increase In Support' For Gay Marriage?

Proponents of same-sex marriage see this year a little differently.

Marty Rouse, a director for the Human Rights Campaign, is calling 2009 a significant year of progress for same-sex marriage, despite those setbacks.

"Public polling shows a clear increase in support for recognition of gay and lesbian couples, and support of marriage equality," Rouse says.

Iowa, Vermont and New Hampshire passed legislation legalizing such unions. But Rouse acknowledges that the issue is a sensitive one even in Washington, D.C., where passage of the measure is all but assured.

"It's the district's business," she says. "It's the right thing to do, and it's my job to make sure Congress does nothing."

She says that the Democrats in charge of Congress believe this is an issue of home rule for Washington, and she believes the same-sex marriage legislation will be enacted as law after a 30-day congressional review period.

It would take a joint resolution of Congress, signed by the president, to overturn the measure once it becomes law. And advocates don't believe that will happen.